1. Field of the Invention
The present invention relates to a thread end holding device for a sewing machine.
2. Description and Problems of the Related Art
A thread end holding device, which is a device provided in a sewing machine equipped with a thread trimming device, pulls out an end of a needle thread above a cloth having been sewn and clamps the same after needle and bobbin threads are cut under the cloth after sewing the cloth is completed, and has a function to prevent the end of the needle thread from being entangled like a bird's nest on the rear side of the cloth when the sewing is resumed for the cloth.
A conventional thread end holding device for a sewing machine, for example, is disclosed in the Japanese Patent Laid-Open Publication No. 2-078177. That is the thread end holding device which is provided on the side of a sewing machine arm 1 and is driven by an electromagnetic solenoid 3 to swing between a lower thread catching position and an upper home position, and which comprises a needle thread catching puller 111 having a hook portion 111A at the tip end thereof for catching a needle thread NT extending from a needle 12 when the thread end holding device is at the thread catching position, and a first and second holding members 114 and 115 respectively fixed to the side of the sewing machine arm 1 for elastically clamping the thread end NTE of the needle thread NT caught by the hook portion 11A therebetween when the needle thread catching puller 111 is at the home position as illustrated in FIGS. 4 and 5. Denoted at 2 is a supporting plate, 3A is the plunger of the electromagnetic solenoid 3, 4 is a supporting shaft, 5 is a connecting link, 6 is a swinging link, 7 is a coiled spring, 8 is a driving link, 9 is a needle thread catching puller supporting shaft, 10 is a driving crank, 13 is a cloth and 16 is a sewing machine bed.
Such a conventional thread end holding device, however, has the following technical problems.
(1) Since the needle thread catching puller 111 has a bent portion 111B to be L-shaped as a whole in a front view as illustrated in FIG. 4, it is impossible to accommodate the needle thread catching puller 111 in the side of the sewing machine arm I when the needle thread catching puller 111 is at its home position so that the sewing machine may be compact in size. Moreover, since the hook portion 111A is located close to the upper surface of a needle throat at its home position, it prevents handling the cloth on the needle throat etc., so that the efficiency of sewing operation is lowered.
(2) Since the needle thread catching puller 111 has the bent portion 111B to be L-shaped in the front view, it is comparatively low in rigidity and inferior in durability. Moreover, since the needle thread catching puller 111 is designed to always engage the clamping portions 114B and 115B of the first and second holding members 114 and 115 at the hook portion 111A thereof, the needle thread catching puller 111 has to have a circular arc shape which has the center thereof at a needle thread catching puller supporting shaft 9 with high accuracy, so that manufacturing the same is not easy.
Furthermore, the first and second holding members 114 and 115 have to be complicated in shape so that they may not interrupt the swinging of the needle thread catching puller 111 about the needle thread catching puller supporting shaft 9. As a result, the clamping portions 114B and 115B can hardly secure the elastic clamping force therebetween stably, are not easy in manufacturing and are inferior both in durability and operational reliability. Still furthermore, it is difficult to give a same shape to the first and second holding members 114 and 115, which makes the manufacturing more troublesome.
(3) A sharp tip end projection 111C is formed so as to form a thread guide portion 111D for pushing off the thread end NTE at the lower portion of the hook portion 111A of the needle thread catching puller 111 as illustrated in FIG. 5, and the sharp tip end projection 111C and the clamping portions 114B and 115B of the first and second holding members 114 and 115 are provided comparatively close to the upper surface of the needle throat of the sewing machine bed 16, so that the cloth or the needle thread is liable to be caught by the tip portions of the needle thread catching puller 111 and the first and second holding members 114 and 115, which prevents the sewing operation when an operator handles the cloth or performs other various operations accompanying the sewing operation, resulting in a technical problem that the production efficiency and safety in sewing operation are lowered.